"""
:mod:`dim` is an HTML parser and simple DOM implementation with CSS
selector support.
:mod:`dim`
- is a single module;
- has no dependency outside `PSL <https://docs.python.org/3/library/>`_;
- is not crazy long;
- supports Python 3.6 and forward,
so the file could be directly embedded in any Python 3.4+ application,
or even in a monolithic source file. :mod:`dim` was designed to ease the
development of `googler(1) <https://github.com/jarun/googler/>`_, which
itself promises to be a single Python script with zero third-party dep.
Simple example:
.. doctest::
>>> import dim
>>> html = '''
... <html>
... <body>
... <table id="primary">
... <thead>
... <tr><th class="bold">A</th><th>B</th></tr>
... </thead>
... <tbody>
... <tr class="highlight"><td class="bold">1</td><td>2</td></tr>
... <tr><td class="bold">3</td><td>4</td></tr>
... <tr><td class="bold">5</td><td>6</td></tr>
... <tr><td class="bold">7</td><td>8</td></tr>
... </tbody>
... </table>
... <table id="secondary">
... <thead>
... <tr><th class="bold">C</th><th>D</th></tr>
... </thead>
... <tbody></tbody>
... </table>
... </body>
... </html>'''
>>> root = dim.parse_html(html)
>>> [elem.text for elem in root.select_all('table#primary th.bold, '
... 'table#primary tr.highlight + tr > td.bold')]
['A', '3']
>>> [elem.text for elem in root.select_all('table#primary th.bold, '
... 'table#primary tr.highlight ~ tr > td.bold')]
['A', '3', '5', '7']
>>> [elem.text for elem in root.select_all('th.bold, tr.highlight ~ tr > td.bold')]
['A', '3', '5', '7', 'C']
"""
import html
import re
from collections import OrderedDict
from enum import Enum
from html.parser import HTMLParser
from typing import (
Any,
Dict,
Generator,
Iterable,
Iterator,
List,
Match,
Optional,
Sequence,
Tuple,
Union,
cast,
)
SelectorGroupLike = Union[str, "SelectorGroup", "Selector"]
[docs]class Node(object):
"""
Represents a DOM node.
Parts of JavaScript's DOM ``Node`` API and ``Element`` API are
mirrored here, with extensions. In particular, ``querySelector`` and
``querySelectorAll`` are mirrored.
Notable properties and methods: :meth:`attr()`, :attr:`classes`,
:attr:`html`, :attr:`text`, :meth:`ancestors()`,
:meth:`descendants()`, :meth:`select()`, :meth:`select_all()`,
:meth:`matched_by()`,
Attributes:
tag (:class:`Optional`\\[:class:`str`])
attrs (:class:`Dict`\\[:class:`str`, :class:`str`])
parent (:class:`Optional`\\[:class:`Node`])
children (:class:`List`\\[:class:`Node`])
"""
# Meant to be reimplemented by subclasses.
def __init__(self) -> None:
self.tag = None # type: Optional[str]
self.attrs = {} # type: Dict[str, str]
self.parent = None # type: Optional[Node]
self.children = [] # type: List[Node]
# Used in DOMBuilder.
self._partial = False
self._namespace = None # type: Optional[str]
# HTML representation of the node. Meant to be implemented by
# subclasses.
def __str__(self) -> str: # pragma: no cover
raise NotImplementedError
[docs] def select(self, selector: SelectorGroupLike) -> Optional["Node"]:
"""DOM ``querySelector`` clone. Returns one match (if any)."""
selector = self._normalize_selector(selector)
for node in self._select_all(selector):
return node
return None
[docs] def query_selector(self, selector: SelectorGroupLike) -> Optional["Node"]:
"""Alias of :meth:`select`."""
return self.select(selector)
[docs] def select_all(self, selector: SelectorGroupLike) -> List["Node"]:
"""DOM ``querySelectorAll`` clone. Returns all matches in a list."""
selector = self._normalize_selector(selector)
return list(self._select_all(selector))
[docs] def query_selector_all(self, selector: SelectorGroupLike) -> List["Node"]:
"""Alias of :meth:`select_all`."""
return self.select_all(selector)
[docs] def matched_by(
self, selector: SelectorGroupLike, root: Optional["Node"] = None
) -> bool:
"""
Checks whether this node is matched by `selector`.
See :meth:`SelectorGroup.matches()`.
"""
selector = self._normalize_selector(selector)
return selector.matches(self, root=root)
@staticmethod
def _normalize_selector(selector: SelectorGroupLike) -> "SelectorGroup":
if isinstance(selector, str):
return SelectorGroup.from_str(selector)
if isinstance(selector, SelectorGroup):
return selector
if isinstance(selector, Selector):
return SelectorGroup([selector])
raise ValueError("not a selector or group of selectors: %s" % repr(selector))
def _select_all(self, selector: "SelectorGroup") -> Generator["Node", None, None]:
for descendant in self.descendants():
if selector.matches(descendant, root=self):
yield descendant
[docs] def child_nodes(self) -> List["Node"]:
return self.children
[docs] def first_child(self) -> Optional["Node"]:
if self.children:
return self.children[0]
else:
return None
[docs] def first_element_child(self) -> Optional["Node"]:
for child in self.children:
if isinstance(child, ElementNode):
return child
return None
[docs] def last_child(self) -> Optional["Node"]:
if self.children:
return self.children[-1]
else:
return None
[docs] def last_element_child(self) -> Optional["Node"]:
for child in reversed(self.children):
if isinstance(child, ElementNode):
return child
return None
[docs] def next_sibling(self) -> Optional["Node"]:
""".. note:: Not O(1), use with caution."""
next_siblings = self.next_siblings()
if next_siblings:
return next_siblings[0]
else:
return None
[docs] def next_siblings(self) -> List["Node"]:
parent = self.parent
if not parent:
return []
try:
index = parent.children.index(self)
return parent.children[index + 1 :]
except ValueError: # pragma: no cover
raise ValueError("node is not found in children of its parent")
[docs] def next_element_sibling(self) -> Optional["ElementNode"]:
""".. note:: Not O(1), use with caution."""
for sibling in self.next_siblings():
if isinstance(sibling, ElementNode):
return sibling
return None
[docs] def previous_sibling(self) -> Optional["Node"]:
""".. note:: Not O(1), use with caution."""
previous_siblings = self.previous_siblings()
if previous_siblings:
return previous_siblings[0]
else:
return None
[docs] def previous_siblings(self) -> List["Node"]:
"""
Compared to the natural DOM order, the order of returned nodes
are reversed. That is, the adjacent sibling (if any) is the
first in the returned list.
"""
parent = self.parent
if not parent:
return []
try:
index = parent.children.index(self)
if index > 0:
return parent.children[index - 1 :: -1]
else:
return []
except ValueError: # pragma: no cover
raise ValueError("node is not found in children of its parent")
[docs] def previous_element_sibling(self) -> Optional["ElementNode"]:
""".. note:: Not O(1), use with caution."""
for sibling in self.previous_siblings():
if isinstance(sibling, ElementNode):
return sibling
return None
[docs] def ancestors(
self, *, root: Optional["Node"] = None
) -> Generator["Node", None, None]:
"""
Ancestors are generated in reverse order of depth, stopping at
`root`.
A :class:`RuntimeException` is raised if `root` is not in the
ancestral chain.
"""
if self is root:
return
ancestor = self.parent
while ancestor is not root:
if ancestor is None:
raise RuntimeError("provided root node not found in ancestral chain")
yield ancestor
ancestor = ancestor.parent
if root:
yield root
[docs] def descendants(self) -> Generator["Node", None, None]:
"""Descendants are generated in depth-first order."""
for child in self.children:
yield child
yield from child.descendants()
[docs] def attr(self, attr: str) -> Optional[str]:
"""Returns the attribute if it exists on the node, otherwise ``None``."""
return self.attrs.get(attr)
@property
def html(self) -> str:
"""
HTML representation of the node.
(For a :class:`TextNode`, :meth:`html` returns the escaped version of the
text.
"""
return str(self)
[docs] def outer_html(self) -> str:
"""Alias of :attr:`html`."""
return self.html
[docs] def inner_html(self) -> str:
"""HTML representation of the node's children."""
return "".join(child.html for child in self.children)
@property
def text(self) -> str: # pragma: no cover
"""This property is expected to be implemented by subclasses."""
raise NotImplementedError
[docs] def text_content(self) -> str:
"""Alias of :attr:`text`."""
return self.text
@property
def classes(self) -> List[str]:
return self.attrs.get("class", "").split()
[docs] def class_list(self) -> List[str]:
return self.classes
[docs]class ElementNode(Node):
"""
Represents an element node.
Note that tag and attribute names are case-insensitive; attribute
values are case-sensitive.
"""
def __init__(
self,
tag: str,
attrs: Iterable[Tuple[str, Optional[str]]],
*,
parent: Optional["Node"] = None,
children: Optional[Sequence["Node"]] = None
) -> None:
Node.__init__(self)
self.tag = tag.lower() # type: str
self.attrs = OrderedDict((attr.lower(), val or "") for attr, val in attrs)
self.parent = parent
self.children = list(children or [])
def __repr__(self) -> str:
s = "<" + self.tag
if self.attrs:
s += " attrs=%s" % repr(list(self.attrs.items()))
if self.children:
s += " children=%s" % repr(self.children)
s += ">"
return s
# https://ipython.readthedocs.io/en/stable/api/generated/IPython.lib.pretty.html
def _repr_pretty_(self, p: Any, cycle: bool) -> None: # pragma: no cover
if cycle:
raise RuntimeError("cycle detected in DOM tree")
p.text("<\x1b[1m%s\x1b[0m" % self.tag)
if self.attrs:
p.text(" attrs=%s" % repr(list(self.attrs.items())))
if self.children:
p.text(" children=[")
if len(self.children) == 1 and isinstance(self.first_child(), TextNode):
p.text("\x1b[4m%s\x1b[0m" % repr(self.first_child()))
else:
with p.indent(2):
for child in self.children:
p.break_()
if hasattr(child, "_repr_pretty_"):
child._repr_pretty_(p, False) # type: ignore
else:
p.text("\x1b[4m%s\x1b[0m" % repr(child))
p.text(",")
p.break_()
p.text("]")
p.text(">")
def __str__(self) -> str:
"""HTML representation of the node."""
s = "<" + self.tag
for attr, val in self.attrs.items():
s += ' %s="%s"' % (attr, html.escape(val))
if self.children:
s += ">"
s += "".join(str(child) for child in self.children)
s += "</%s>" % self.tag
else:
if _tag_is_void(self.tag):
s += "/>"
else:
s += "></%s>" % self.tag
return s
@property
def text(self) -> str:
"""The concatenation of all descendant text nodes."""
return "".join(child.text for child in self.children)
[docs]class TextNode(str, Node):
"""
Represents a text node.
Subclasses :class:`Node` and :class:`str`.
"""
def __new__(cls, text: str) -> "TextNode":
s = str.__new__(cls, text) # type: ignore
s.parent = None
return s # type: ignore
def __init__(self, text: str) -> None:
Node.__init__(self)
def __repr__(self) -> str:
return "<%s>" % str.__repr__(self)
# HTML-escaped form of the text node. use text() for unescaped
# version.
def __str__(self) -> str:
return html.escape(self)
[docs] def __eq__(self, other: object) -> bool:
"""
Two text nodes are equal if and only if they are the same node.
For string comparison, use :attr:`text`.
"""
return self is other
[docs] def __ne__(self, other: object) -> bool:
"""
Two text nodes are non-equal if they are not the same node.
For string comparison, use :attr:`text`.
"""
return self is not other
@property
def text(self) -> str:
return str.__str__(self)
[docs]class DOMBuilderException(Exception):
"""
Exception raised when :class:`DOMBuilder` detects a bad state.
Attributes:
pos (:class:`Tuple`\\[:class:`int`, :class:`int`]):
Line number and offset in HTML input.
why (:class:`str`):
Reason of the exception.
"""
def __init__(self, pos: Tuple[int, int], why: str) -> None:
self.pos = pos
self.why = why
def __str__(self) -> str: # pragma: no cover
return "DOM builder aborted at %d:%d: %s" % (self.pos[0], self.pos[1], self.why)
[docs]class DOMBuilder(HTMLParser):
"""
HTML parser / DOM builder.
Subclasses :class:`html.parser.HTMLParser`.
Consume HTML and builds a :class:`Node` tree. Once finished, use
:attr:`root` to access the root of the tree.
This parser cannot parse malformed HTML with tag mismatch.
"""
def __init__(self) -> None:
super().__init__(convert_charrefs=True)
# _stack is the stack for nodes. Each node is pushed to the
# stack when its start tag is processed, and remains on the
# stack until its parent node is completed (end tag processed),
# at which point the node is attached to the parent node as a
# child and popped from the stack.
self._stack = [] # type: List[Node]
# _namespace_stack is another stack tracking the parsing
# context, which is generally the default namespace (None) but
# changes when parsing foreign objects (e.g. 'svg' when parsing
# an <svg>). The top element is always the current parsing
# context, so popping works differently from _stack: an element
# is popped as soon as the corresponding end tag is processed.
self._namespace_stack = [None] # type: List[Optional[str]]
[docs] def handle_starttag(
self, tag: str, attrs: Sequence[Tuple[str, Optional[str]]]
) -> None:
node = ElementNode(tag, attrs)
node._partial = True
self._stack.append(node)
namespace = (
tag.lower()
if _tag_encloses_foreign_namespace(tag)
else self._namespace_stack[-1] # Inherit parent namespace
)
node._namespace = namespace
self._namespace_stack.append(namespace)
# For void elements (not in a foreign context), immediately
# invoke the end tag handler (see handle_startendtag()).
if not namespace and _tag_is_void(tag):
self.handle_endtag(tag)
[docs] def handle_endtag(self, tag: str) -> None:
tag = tag.lower()
children = []
while self._stack and not self._stack[-1]._partial:
children.append(self._stack.pop())
if not self._stack:
raise DOMBuilderException(self.getpos(), "extra end tag: %s" % repr(tag))
parent = self._stack[-1]
if parent.tag != tag:
raise DOMBuilderException(
self.getpos(),
"expecting end tag %s, got %s" % (repr(parent.tag), repr(tag)),
)
parent.children = list(reversed(children))
parent._partial = False
for child in children:
child.parent = parent
self._namespace_stack.pop()
# Make parser behavior for explicitly and implicitly void elements
# (e.g., <hr> vs <hr/>) consistent. The former triggers
# handle_starttag only, whereas the latter triggers
# handle_startendtag (which by default triggers both handle_starttag
# and handle_endtag). See https://bugs.python.org/issue25258.
#
# An exception is foreign elements, which aren't considered void
# elements but can be explicitly marked as self-closing according to
# the HTML spec (e.g. <path/> is valid but <path> is not).
# Therefore, both handle_starttag and handle_endtag must be called,
# and handle_endtag should not be triggered from within
# handle_starttag in that case.
#
# Note that for simplicity we do not check whether the foreign
# element in question is allowed to be self-closing by spec. (The
# SVG spec unfortunately doesn't provide a readily available list of
# such elements.)
#
# https://html.spec.whatwg.org/multipage/syntax.html#foreign-elements
[docs] def handle_startendtag(
self, tag: str, attrs: Sequence[Tuple[str, Optional[str]]]
) -> None:
if self._namespace_stack[-1] or _tag_encloses_foreign_namespace(tag):
self.handle_starttag(tag, attrs)
self.handle_endtag(tag)
else:
self.handle_starttag(tag, attrs)
[docs] def handle_data(self, text: str) -> None:
if not self._stack:
# Ignore text nodes before the first tag.
return
self._stack.append(TextNode(text))
@property
def root(self) -> "Node":
"""
Finishes processing and returns the root node.
Raises :class:`DOMBuilderException` if there is no root tag or
root tag is not closed yet.
"""
if not self._stack:
raise DOMBuilderException(self.getpos(), "no root tag")
if self._stack[0]._partial:
raise DOMBuilderException(self.getpos(), "root tag not closed yet")
return self._stack[0]
[docs]def parse_html(html: str, *, ParserClass: type = DOMBuilder) -> "Node":
"""
Parses HTML string, builds DOM, and returns root node.
The parser may raise :class:`DOMBuilderException`.
Args:
html: input HTML string
ParserClass: :class:`DOMBuilder` or a subclass
Returns:
Root note of the parsed tree. If the HTML string contains
multiple top-level elements, only the first is returned and the
rest are lost.
"""
builder = ParserClass() # type: DOMBuilder
builder.feed(html)
builder.close()
return builder.root
[docs]class SelectorParserException(Exception):
"""
Exception raised when the selector parser fails to parse an input.
Attributes:
s (:class:`str`):
The input string to be parsed.
cursor (:class:`int`):
Cursor position where the failure occurred.
why (:class:`str`):
Reason of the failure.
"""
def __init__(self, s: str, cursor: int, why: str) -> None:
self.s = s
self.cursor = cursor
self.why = why
def __str__(self) -> str: # pragma: no cover
return "selector parser aborted at character %d of %s: %s" % (
self.cursor,
repr(self.s),
self.why,
)
[docs]class SelectorGroup:
"""
Represents a group of CSS selectors.
A group of CSS selectors is simply a comma-separated list of
selectors. [#]_ See :class:`Selector` documentation for the scope of
support.
Typically, a :class:`SelectorGroup` is constructed from a string
(e.g., ``th.center, td.center``) using the factory function
:meth:`from_str`.
.. [#] https://www.w3.org/TR/selectors-3/#grouping
"""
def __init__(self, selectors: Iterable["Selector"]) -> None:
self._selectors = list(selectors)
def __repr__(self) -> str:
return "<SelectorGroup %s>" % repr(str(self))
def __str__(self) -> str:
return ", ".join(str(selector) for selector in self._selectors)
[docs] def __len__(self) -> int:
return len(self._selectors)
[docs] def __getitem__(self, index: int) -> "Selector":
return self._selectors[index]
[docs] def __iter__(self) -> Iterator["Selector"]:
return iter(self._selectors)
[docs] @classmethod
def from_str(cls, s: str) -> "SelectorGroup":
"""
Parses input string into a group of selectors.
:class:`SelectorParserException` is raised on invalid input. See
:class:`Selector` documentation for the scope of support.
Args:
s: input string
Returns:
Parsed group of selectors.
"""
i = 0
selectors = []
while i < len(s):
selector, i = Selector.from_str(s, i)
selectors.append(selector)
if not selectors:
raise SelectorParserException(s, i, "selector group is empty")
return cls(selectors)
[docs] def matches(self, node: "Node", root: Optional["Node"] = None) -> bool:
"""
Decides whether the group of selectors matches `node`.
The group of selectors matches `node` as long as one of the
selectors matches `node`.
If `root` is provided and child and/or descendant combinators
are involved, parent/ancestor lookup terminates at `root`.
"""
return any(selector.matches(node, root=root) for selector in self)
[docs]class Selector:
"""
Represents a CSS selector.
Recall that a CSS selector is a chain of one or more *sequences of
simple selectors* separated by *combinators*. [#selectors-3]_ This
concept is represented as a cons list of sequences of simple
selectors (in right to left order). This class in fact holds a
single sequence, with an optional combinator and reference to the
previous sequence.
For instance, ``main#main p.important.definition >
a.term[id][href]`` would be parsed into (schematically) the
following structure::
">" tag='a' classes=('term') attrs=([id], [href]) ~>
" " tag='p' classes=('important', 'definition') ~>
tag='main' id='main'
Each line is held in a separate instance of :class:`Selector`,
linked together by the :attr:`previous` attribute.
Supported grammar (from selectors level 3 [#selectors-3]_):
- Type selectors;
- Universal selectors;
- Class selectors;
- ID selectors;
- Attribute selectors;
- Combinators.
Unsupported grammar:
- Pseudo-classes;
- Pseudo-elements;
- Namespace prefixes (``ns|``, ``*|``, ``|``) in any part of any
selector.
Rationale:
- Pseudo-classes have too many variants, a few of which even
complete with an admittedly not-so-complex minilanguage. These add
up to a lot of code.
- Pseudo-elements are useless outside rendering contexts, hence out of
scope.
- Namespace support is too niche to be worth the parsing headache.
*Using namespace prefixes may confuse the parser!*
Note that the parser only loosely follows the spec and priotizes
ease of parsing (which includes readability and *writability* of
regexes), so some invalid selectors may be accepted (in fact, false
positives abound, but accepting valid inputs is a much more
important goal than rejecting invalid inputs for this library), and
some valid selectors may be rejected (but as long as you stick to
the scope outlined above and common sense you should be fine; the
false negatives shouldn't be used by actual human beings anyway).
In particular, whitespace character is simplified to ``\\s`` (ASCII
mode) despite CSS spec not counting U+000B (VT) as whitespace,
identifiers are simplified to ``[\\w-]+`` (ASCII mode), and strings
(attribute selector values can be either identifiers or strings)
allow escaped quotes (i.e., ``\\'`` inside single-quoted strings and
``\\"`` inside double-quoted strings) but everything else is
interpreted literally. The exact specs for CSS identifiers and
strings can be found at [#]_.
Certain selectors and combinators may be implemented in the parser
but not implemented in matching and/or selection APIs.
.. [#selectors-3] https://www.w3.org/TR/selectors-3/
.. [#] https://www.w3.org/TR/CSS21/syndata.html
Attributes:
tag (:class:`Optional`\\[:class:`str`]):
Type selector.
classes (:class:`List`\\[:class:`str`]):
Class selectors.
id (:class:`Optional`\\[:class:`str`]):
ID selector.
attrs (:class:`List`\\[:class:`AttributeSelector`]):
Attribute selectors.
combinator (:class:`Optional`\\[:class:`Combinator`]):
Combinator with the previous sequence of simple selectors in
chain.
previous (:class:`Optional`\\[:class:`Selector`]):
Reference to the previous sequence of simple selectors in
chain.
"""
def __init__(
self,
*,
tag: Optional[str] = None,
classes: Optional[Sequence[str]] = None,
id: Optional[str] = None,
attrs: Optional[Sequence["AttributeSelector"]] = None,
combinator: Optional["Combinator"] = None,
previous: Optional["Selector"] = None
) -> None:
self.tag = tag.lower() if tag else None
self.classes = list(classes or [])
self.id = id
self.attrs = list(attrs or [])
self.combinator = combinator
self.previous = previous
def __repr__(self) -> str:
return "<Selector %s>" % repr(str(self))
def __str__(self) -> str:
sequences = []
delimiters = []
seq = self
while True:
sequences.append(seq._sequence_str_())
if seq.previous:
if seq.combinator == Combinator.DESCENDANT:
delimiters.append(" ")
elif seq.combinator == Combinator.CHILD:
delimiters.append(" > ")
elif seq.combinator == Combinator.NEXT_SIBLING:
delimiters.append(" + ")
elif seq.combinator == Combinator.SUBSEQUENT_SIBLING:
delimiters.append(" ~ ")
else: # pragma: no cover
raise RuntimeError(
"unimplemented combinator: %s" % repr(self.combinator)
)
seq = seq.previous
else:
delimiters.append("")
break
return "".join(
delimiter + sequence
for delimiter, sequence in zip(reversed(delimiters), reversed(sequences))
)
# Format a single sequence of simple selectors, without combinator.
def _sequence_str_(self) -> str:
s = ""
if self.tag:
s += self.tag
if self.classes:
s += "".join(".%s" % class_ for class_ in self.classes)
if self.id:
s += "#%s" % self.id
if self.attrs:
s += "".join(str(attr) for attr in self.attrs)
return s if s else "*"
[docs] @classmethod
def from_str(cls, s: str, cursor: int = 0) -> Tuple["Selector", int]:
"""
Parses input string into selector.
This factory function only parses out one selector (up to a
comma or EOS), so partial consumption is allowed --- an optional
`cursor` is taken as input (0 by default) and the moved cursor
(either after the comma or at EOS) is returned as part of the
output.
:class:`SelectorParserException` is raised on invalid input. See
:class:`Selector` documentation for the scope of support.
If you need to completely consume a string representing
(potentially) a group of selectors, use
:meth:`SelectorGroup.from_str()`.
Args:
s: input string
cursor: initial cursor position on `s`
Returns:
A tuple containing the parsed selector and the moved the
cursor (either after a comma-delimiter, or at EOS).
"""
# Simple selectors.
TYPE_SEL = re.compile(r"[\w-]+", re.A)
UNIVERSAL_SEL = re.compile(r"\*")
ATTR_SEL = re.compile(
r"""\[
\s*(?P<attr>[\w-]+)\s*
(
(?P<op>[~|^$*]?=)\s*
(
(?P<val_identifier>[\w-]+)|
(?P<val_string>
(?P<quote>['"])
(?P<val_string_inner>.*?)
(?<!\\)(?P=quote)
)
)\s*
)?
\]""",
re.A | re.X,
)
CLASS_SEL = re.compile(r"\.([\w-]+)", re.A)
ID_SEL = re.compile(r"#([\w-]+)", re.A)
PSEUDO_CLASS_SEL = re.compile(r":[\w-]+(\([^)]+\))?", re.A)
PSEUDO_ELEM_SEL = re.compile(r"::[\w-]+", re.A)
# Combinators
DESCENDANT_COM = re.compile(r"\s+")
CHILD_COM = re.compile(r"\s*>\s*")
NEXT_SIB_COM = re.compile(r"\s*\+\s*")
SUB_SIB_COM = re.compile(r"\s*~\s*")
# Misc
WHITESPACE = re.compile(r"\s*")
END_OF_SELECTOR = re.compile(r"\s*($|,)")
tag = None
classes = []
id = None
attrs = []
combinator = None
selector = None
previous_combinator = None
i = cursor
# Skip leading whitespace
m = WHITESPACE.match(s, i)
if m:
i = m.end()
while i < len(s):
# Parse one simple selector.
#
# PEP 572 (assignment expressions; the one that burned Guido
# so much that he resigned as BDFL) would have been nice; it
# would have saved us from all the regex match
# reassignments, and worse still, the casts, since mypy
# complains about getting Optional[Match[str]] instead of
# Match[str].
if TYPE_SEL.match(s, i):
if tag:
raise SelectorParserException(s, i, "multiple type selectors found")
m = cast(Match[str], TYPE_SEL.match(s, i))
tag = m.group()
elif UNIVERSAL_SEL.match(s, i):
m = cast(Match[str], UNIVERSAL_SEL.match(s, i))
elif ATTR_SEL.match(s, i):
m = cast(Match[str], ATTR_SEL.match(s, i))
attr = m.group("attr")
op = m.group("op")
val_identifier = m.group("val_identifier")
quote = m.group("quote")
val_string_inner = m.group("val_string_inner")
if val_identifier is not None:
val = val_identifier
elif val_string_inner is not None:
val = val_string_inner.replace("\\" + quote, quote)
else:
val = None
if op is None:
type = AttributeSelectorType.BARE
elif op == "=":
type = AttributeSelectorType.EQUAL
elif op == "~=":
type = AttributeSelectorType.TILDE
elif op == "|=":
type = AttributeSelectorType.PIPE
elif op == "^=":
type = AttributeSelectorType.CARET
elif op == "$=":
type = AttributeSelectorType.DOLLAR
elif op == "*=":
type = AttributeSelectorType.ASTERISK
else: # pragma: no cover
raise SelectorParserException(
s,
i,
"unrecognized operator %s in attribute selector" % repr(op),
)
attrs.append(AttributeSelector(attr, val, type))
elif CLASS_SEL.match(s, i):
m = cast(Match[str], CLASS_SEL.match(s, i))
classes.append(m.group(1))
elif ID_SEL.match(s, i):
if id:
raise SelectorParserException(s, i, "multiple id selectors found")
m = cast(Match[str], ID_SEL.match(s, i))
id = m.group(1)
elif PSEUDO_CLASS_SEL.match(s, i):
raise SelectorParserException(s, i, "pseudo-classes not supported")
elif PSEUDO_ELEM_SEL.match(s, i):
raise SelectorParserException(s, i, "pseudo-elements not supported")
else:
raise SelectorParserException(
s, i, "expecting simple selector, found none"
)
i = m.end()
# Try to parse a combinator, or end the selector.
if CHILD_COM.match(s, i):
m = cast(Match[str], CHILD_COM.match(s, i))
combinator = Combinator.CHILD
elif NEXT_SIB_COM.match(s, i):
m = cast(Match[str], NEXT_SIB_COM.match(s, i))
combinator = Combinator.NEXT_SIBLING
elif SUB_SIB_COM.match(s, i):
m = cast(Match[str], SUB_SIB_COM.match(s, i))
combinator = Combinator.SUBSEQUENT_SIBLING
elif END_OF_SELECTOR.match(s, i):
m = cast(Match[str], END_OF_SELECTOR.match(s, i))
combinator = None
# Need to parse descendant combinator at the very end
# because it could be a prefix to all previous cases.
elif DESCENDANT_COM.match(s, i):
m = cast(Match[str], DESCENDANT_COM.match(s, i))
combinator = Combinator.DESCENDANT
else:
continue
i = m.end()
if combinator and i == len(s):
raise SelectorParserException(s, i, "unexpected end at combinator")
selector = cls(
tag=tag,
classes=classes,
id=id,
attrs=attrs,
combinator=previous_combinator,
previous=selector,
)
previous_combinator = combinator
# End of selector.
if combinator is None:
break
tag = None
classes = []
id = None
attrs = []
combinator = None
if not selector:
raise SelectorParserException(s, i, "selector is empty")
return selector, i
[docs] def matches(self, node: "Node", root: Optional["Node"] = None) -> bool:
"""
Decides whether the selector matches `node`.
Each sequence of simple selectors in the selector's chain must
be matched for a positive.
If `root` is provided and child and/or descendant combinators
are involved, parent/ancestor lookup terminates at `root`.
"""
if self.tag:
if not node.tag or node.tag != self.tag:
return False
if self.id:
if node.attrs.get("id") != self.id:
return False
if self.classes:
classes = node.classes
for class_ in self.classes:
if class_ not in classes:
return False
if self.attrs:
for attr_selector in self.attrs:
if not attr_selector.matches(node):
return False
if not self.previous:
return True
if self.combinator == Combinator.DESCENDANT:
return any(
self.previous.matches(ancestor, root=root)
for ancestor in node.ancestors()
)
elif self.combinator == Combinator.CHILD:
if node is root or node.parent is None:
return False
else:
return self.previous.matches(node.parent)
elif self.combinator == Combinator.NEXT_SIBLING:
sibling = node.previous_element_sibling()
if not sibling:
return False
else:
return self.previous.matches(sibling)
elif self.combinator == Combinator.SUBSEQUENT_SIBLING:
return any(
self.previous.matches(sibling, root=root)
for sibling in node.previous_siblings()
if isinstance(sibling, ElementNode)
)
else: # pragma: no cover
raise RuntimeError("unimplemented combinator: %s" % repr(self.combinator))
[docs]class AttributeSelector:
"""
Represents an attribute selector.
Attributes:
attr (:class:`str`)
val (:class:`Optional`\\[:class:`str`])
type (:class:`AttributeSelectorType`)
"""
def __init__(
self, attr: str, val: Optional[str], type: "AttributeSelectorType"
) -> None:
self.attr = attr.lower()
self.val = val
self.type = type
def __repr__(self) -> str:
return "<AttributeSelector %s>" % repr(str(self))
def __str__(self) -> str:
if self.type == AttributeSelectorType.BARE:
fmt = "[{attr}{val:.0}]"
elif self.type == AttributeSelectorType.EQUAL:
fmt = "[{attr}={val}]"
elif self.type == AttributeSelectorType.TILDE:
fmt = "[{attr}~={val}]"
elif self.type == AttributeSelectorType.PIPE:
fmt = "[{attr}|={val}]"
elif self.type == AttributeSelectorType.CARET:
fmt = "[{attr}^={val}]"
elif self.type == AttributeSelectorType.DOLLAR:
fmt = "[{attr}$={val}]"
elif self.type == AttributeSelectorType.ASTERISK:
fmt = "[{attr}*={val}]"
return fmt.format(attr=self.attr, val=repr(self.val))
[docs] def matches(self, node: "Node") -> bool:
val = node.attrs.get(self.attr)
if val is None:
return False
if self.type == AttributeSelectorType.BARE:
return True
elif self.type == AttributeSelectorType.EQUAL:
return val == self.val
elif self.type == AttributeSelectorType.TILDE:
return self.val in val.split()
elif self.type == AttributeSelectorType.PIPE:
return val == self.val or val.startswith("%s-" % self.val)
elif self.type == AttributeSelectorType.CARET:
return bool(self.val and val.startswith(self.val))
elif self.type == AttributeSelectorType.DOLLAR:
return bool(self.val and val.endswith(self.val))
elif self.type == AttributeSelectorType.ASTERISK:
return bool(self.val and self.val in val)
else: # pragma: no cover
raise RuntimeError("unimplemented attribute selector: %s" % repr(self.type))
# Enum: basis for poor man's algebraic data type.
[docs]class AttributeSelectorType(Enum):
"""
Attribute selector types.
Members correspond to the following forms of attribute selector:
- :attr:`BARE`: ``[attr]``;
- :attr:`EQUAL`: ``[attr=val]``;
- :attr:`TILDE`: ``[attr~=val]``;
- :attr:`PIPE`: ``[attr|=val]``;
- :attr:`CARET`: ``[attr^=val]``;
- :attr:`DOLLAR`: ``[attr$=val]``;
- :attr:`ASTERISK`: ``[attr*=val]``.
"""
# [attr]
BARE = 1
# [attr=val]
EQUAL = 2
# [attr~=val]
TILDE = 3
# [attr|=val]
PIPE = 4
# [attr^=val]
CARET = 5
# [attr$=val]
DOLLAR = 6
# [attr*=val]
ASTERISK = 7
[docs]class Combinator(Enum):
"""
Combinator types.
Members correspond to the following combinators:
- :attr:`DESCENDANT`: ``A B``;
- :attr:`CHILD`: ``A > B``;
- :attr:`NEXT_SIBLING`: ``A + B``;
- :attr:`SUBSEQUENT_SIBLING`: ``A ~ B``.
"""
# ' '
DESCENDANT = 1
# >
CHILD = 2
# +
NEXT_SIBLING = 3
# ~
SUBSEQUENT_SIBLING = 4
def _tag_is_void(tag: str) -> bool:
"""
Checks whether the tag corresponds to a void element.
https://www.w3.org/TR/html5/syntax.html#void-elements
https://html.spec.whatwg.org/multipage/syntax.html#void-elements
"""
return tag.lower() in (
"area",
"base",
"br",
"col",
"embed",
"hr",
"img",
"input",
"link",
"meta",
"param",
"source",
"track",
"wbr",
)
def _tag_encloses_foreign_namespace(tag: str) -> bool:
"""
Checks whether the tag encloses a foreign namespace (MathML or SVG).
https://html.spec.whatwg.org/multipage/syntax.html#foreign-elements
"""
return tag.lower() in ("math", "svg")
